gasket match?

[93GAGT3300]

hi folks, i need some help here.

i'm doing an intake manifold swap on my 96 3100. i was lucky to have spare parts from another motor to help me with this conversion.

my original 96 was a roller rocker motor while the one i'm using isn't. no biggie. the heads have the slot for the roller rocker conversion.

my REAL problem is, i'm using the 2000 mailbu 3100 intake. everything is going well. i'd like to know how do you line up the lower intake manifold to the head, so that you can gasket match the lower intake manifold?!

i already preinstalled the gasket on the head, made my scribe marks on the head, and matched the head to the gasket, but how do you do the lower manifold to the gasket?

help is needed here. i don't want to cut off any unecessary metal, if i can avoid it....... thanks

[ForcedFirebird]

Same way you did on the heads. Place the gasket on there and scribe.

I would like to see pics of this, I'm also curious to see what kind of gains you produced. You probably would have been better off using later heads.

[93GAGT3300]

forced firebird,

thanks for the reply, but there is one slight glitch with doing it that way. the gaskets have little dowel pins that faced the head?!!! that's what made doing the head side a no brainer.

yet, while typing this. it just dawned on me. either (a) get a set of used gaskets, drill through the dowel pin so that i can use that as a marker for the lower intake side. (b) take measurements from the existing gen II 3100 gaskets and plot the dowels hole on the intake.

either way it'll be interesting. yet, you opened my mind to some other ideas.

i'll see if i can take some pics for you. i'll tell you this much . using the 2000+ 3100 intake raised the intake port roof when porting the 96 style head. i think the las four numbers on my head are 3769.

we'll se how it goes.

[ForcedFirebird]

You can use the bolts to line them up as well .

[93GAGT3300]

estimated that too. yet, the bolts are actually smaller that the hole they slide through. i guess that give the intake room for fitment. doing the lower is going to be interesting

[IsaacHayes]

If you are worried about causing turbulence, don't port the LIM bottom ports. Since you already ported the heads, they will have a larger area, and the LIM will have smaller hole/area. It will flow into there without hitting a lip that way. That or center the gasket as best as possible and just even up the ports without doing a full gasket match if you are worried.

So you're using 95 heads then I guess to port and will take off your 96 heads? Yeah if they have notches just swap the rockers and all that over. Otherwise non-roller rockers will need the LIM clearanced for them.

[ForcedFirebird]

If you are worried about causing turbulence, don't port the LIM bottom ports. Since you already ported the heads, they will have a larger area, and the LIM will have smaller hole/area. It will flow into there without hitting a lip that way. That or center the gasket as best as possible and just even up the ports without doing a full gasket match if you are worried.

That will still cause turbulance, as there would be a swirl created behind that small lip. How much would be the question.

So you're using 95 heads then I guess to port and will take off your 96 heads? Yeah if they have notches just swap the rockers and all that over.

I just took apart a 95 to get the pushrod guides to convert my 3500 heads to adjustable rockers (and use 1.7 Ford roller tips ), but I can't remember if I saw the notches or not.

[IsaacHayes]

Yes it's not optimal, but probably better than a large port dumping into a smaller port with a "flat ledge" there. Picture putting a larger TB on a plenum without opening the plenum to match. Now picture a larger plenum opening with a smaller TB. Not as bad of a scenario... Even some engines from the factory have a lot bigger plenum openings compared to the TB opening.

I would think the swirl behind the lip wouldn't affect flow that much since it would cause the effect you see with truck beds with the tail gate up. The air swirls behind the cab and the air over the top of the truck flows over it smoothly. It's probably not optimal but better than having the swirl and lip/ledge in the direct path of flow.

Some 95 heads had notches and some did not. Just depends on the cast used. They all had non-roller rockers however. So some people with 95's with the notch casts are lucky and can swap over to the roller fulcrum rockers.

[ForcedFirebird]

Oh yeah, that reminds me, I have a complete set of 1.6 (or is it 1.65?) rocker from a 3500 that i won't be using either.

[93GAGT3300]

just got home. pulled off both heads and gasket matched the exhaust ports and intake ports. i'm in the garage cleaning the deck surface of the head so i can reinstall them tomorrow.

i was fortunate to have the heads with the notch even though it came with non roller rockers. the swap will go easy. i was comparing the small port intake gasket to the large port intake gasket.

most of the difference between the two gaskets is at the roof side of the gasket. the large port gasket roof is higher than the small port. when i gasket matched the heads, the air now has more of a straighter shot to the valves.

unfortunately, my digital camera is dead and i can't find the power cord. i'll see if i find it later. i haven't ported the lower intake manifold yet. i read the replies which is making me think some more on what to do. i'll keep you posted.

[93GAGT3300]

got off work, went to work on the 3100.

the heads came out nice after i throughly cleaned the deck surface. checked them for flatness, everything was lovely.

wiped down all the mating surfaces with lacquer thinner. removed any residue that was left from cleaning. installed the head back onto the block.

got out the 3100 big port intake manifold lower gasket. used it as a template to port the lower intake manifold. used the old gasket marks as reference points to line it up. scribed the new marks and ported away. made sure not to go to close to the scribe marks in case the alignment was a hair off.

put a little ultra black sealant around the water outlet ports, and installed the gasket.

pulled roller fulcrum rockers, pedestals, bolts and pushrods out of the carburetor cleaner tank. man, they came out spotless.

pre installed all parts to check for fitment.

cleaned lower intake manifold for final installation tomorrow.

the upper manifold and accessories will be a cake walk.

[geoffinbc]

The purpose of a port match is to align the ports. None of you guys have mentioned a method to verify alignment. The gasket needs to be coated with blue dye or prussian blue in order to get an imprint of where the head and intake are actually meeting. When you disassemble the intake from the heads the dye markings can be used to trim the gasket which you use as a template to determine where to grind on both the head and intake side in order to get proper alignment. Then once the openings match you need to blend this into the ports.

If the heads or block are ever milled in the future this process needs to be repeated.

[93GAGT3300]

thanks for the reply betterthanyou.

everything you stated was true. i'm familiar with the prussian blue process.

yet, at the moment $$$$ is tight. between my quad 4, and this conversion i'm surprised i haven't gone broke.

had i gone that route, i'd need another set of gaskets to do this throughly. i'm not denying at all what you stated insn't true. yet, this was an emergency fix for one motor than ended up turning into a top end conversion.

i figured hell, if i'm in here now i might as well do the best i can.

[93GAGT3300]

forgot to state, the lower intake manifold is on?!!!!!!

everything went together nicely. lubed the rockers, pushrods and torqued to spec.

throughly cleaned the lower intake manifold, bolts and etc. installed the lower intake manifold.

i was contemplating porting the upper to lower intake manifold ports. yet, when i noticed how close of a match they were, i opted not to.

the upper intake manifold i painted black. i may paint the rocker covers too since i have them soaking to get cleaned up.

after i button up the motor. i have to finish reinstalling the rest of the stuff i took out of the engione compartment, then off we go.......

i think down the road there may be a cam swap depending on how it responds to what i've done.....

[93GAGT3300]

well, the lower intake is back on.

so, i started putting on new injector o-rings when something dawned on me. i could see the lower manifold mated to the head through the injector hole?! sure enough, i could see the head the gasket, and the lower manifold, all where it lined up.

i have to save with the help of a very tiny flashlight that looked more like a probe, i could see how it lined up. i could see the roof, but the sides and the bottm all lined up nicely. i was quite pleased to know this.

installed the injector asm, bolted it back to the lower intake manifold. washed the valve covers and painted those too.

i have to repaint the upper intake manifold. there were some spots that i missed.

we'll see what happens tomorrow.